1. Field of the Invention
The invention relates to a method for transporting sheets which are conveyed successively to a stop unit and are held there until a stack is formed which is comprised of at least one sheet which stack is subsequently transported farther by the stop unit. The invention also relates to a device for performing the method, wherein the device comprises transport elements, preferably transport belts, for the sheets, and a stop unit which is positioned in the transport path of the sheets and can be driven in a cycled fashion and is connected to a control device.
2. Description of the Related Art
In a known device of this kind, the sheets are supplied by a feeder. In the feeder, the sheets are stacked and are then individually gripped by rollers and read. The sheets are transported by the transport elements to the stop unit where they are held until the sheets coming from the feeder stack have been compiled as sets. As soon as these sheet sets or sheet stacks have been generated, the stop unit is switched on so that this set of sheets is transported to a processing station arranged downstream. When switching on the stop unit, the feeder is also switched on so that the sheets of the next set to be formed are transported to the stop unit. As soon as the previously formed stack has been transported away, the stop unit is switched off so that the subsequently arriving sheets coming from the feeder again can form a stack at the stop unit. In this way, the corresponding sheet sets at the stop unit are formed successively and are then transported in a cycled fashion. The sheet sets are formed with considerable temporal spacing successively at the stop unit and then further transported by it. With this procedure and device it is therefore not possible to achieve high output.
It is an object of the present invention to further develop the method according to the aforementioned kind such that a high output can be achieved without compromising the reliability of the sheet feeding action.
In accordance with the present invention, this is achieved in that the further transport of the sheet stack is carried out as soon as a sheet of the next stack to be formed overlaps the sheet stack resting against the stop unit. With respect to the device this is achieved in that the control device has a sensor device connected thereto which during transport of a sheet, belonging to the stack to be newly formed, sends a signal for switching on the stop unit when the transported sheet overlaps the stack resting against the stop unit.
In the method according to the invention the further transport of the stack formed at the stop unit and the feeding of the sheet of the next stack to be formed are carried out so that overlap occurs. Accordingly, during the stack formation there is no delay, resulting from the wait for the finished stack to be transported farther by the stop unit, before the first sheet of the next stack to be formed is supplied. The further transport of the stack formed at the stop unit is carried out as soon as the first sheet of the respective next stack to be formed overlaps the stack resting against the stop unit. In this way, very high cycle times and thus very high output is produced. The device according to the invention has a sensor device which, during the transport of the sheet belonging to the next stack to be formed, supplies a signal for switching on the stop unit when this sheet overlaps the finished stack resting against the stop unit. Because of this embodiment the device according to the invention has a high output.
In the simplest case, the stack (set) is comprised of only a single sheet. Of course, the stack can also be comprised of two or more sheets.